It is known in the art to bond one fabric to another by interfeeding a solid adhesive therebetween followed by the application of heat.
U.S. Pat. No. 3,607,554 issued to W. R. Heffernan illustrates one such bonding method and an apparatus therefor. In the Heffernan method two layers of sheet material are joined along a narrow two-dimensional contour by laying a thermally active adhesive between the two layers and applying heat so as to cause the adhesive to liquify. The essence of that invention lies in the use of a pivot means which applies constant pressure to the fabric along a narrow contour or path so as to effect a bonding of the two layers along that contour.
According to Heffernan the adhesive is made to liquify by passing the layers of fabric and adhesive between an upper electrode and a lower electrode which are activated by a radio frequency field. The resulting field and the compressive force of the two electrodes causes the melted adhesive to flow and results in a bonding of the two layers.
The Heffernan operation is a suitable one for joining fabrics which can be conveyed by a moving belt but drapery material which can measure up to 50 feet or more in height, does not fall into the category.
Furthermore, the compressive force on the material to be joined in the Heffernan process includes pressure exerted by a pivot pin on the upper surface of said material. This pivot pin is in constant contact with the material and thus applies constant pressure. Consequently, when the pressure from the electrodes is released the continuing pressure from the pivot pin will still allow the operator to control the material by pivoting it about the pin. As a result, the materials can be joined along a narrow two-dimensional contour equivalent to the width of said pivot pin.
Again, drapery material is of such size and bulk that, as a practical matter, it cannot be pivoted during the bonding operation. Furthermore, the Heffernan method of joining fabrics along a narrow contour makes it unsuitable for tableing draperies because the area thus joined would not be of sufficient size as to provide a suitably pleatable area.
The narrow contour envisioned by Heffernan is an extremely narrow strip of joined fabric. By contrast, the crinoline-backed area on draperies is generally in the range of from about 3 to 5 inches in width. A crinoline backing of lesser dimension would simply fail to provide the area needed to create a shirred or pleated effect.
Another method for bonding fabrics via the use of an adhesive is described in U.S. Pat. No. 3,738,897 to G. Bianchini. In this method an interlining is secured between two fabrics by interfeeding an adhesive tape and subjecting the several layers to heat, pressure and cooling.
According to Bianchini the fabrics to be joined are placed on a conveyer belt with the adhesive therebetween and this multilayered sheet is transported to an area where heat is applied to the top and bottom surfaces thereof; to the top side thereof from an infrared source and to the bottom side thereof from a heat box. The coupled fabrics are then driven between pairs of pressure rollers and subjected to a flow of cool air which is blown across the face of the fabric to prevent calendering.
Obviously, the Bianchini process does not lend itself to the manufacture of draperies. In Bianchini the materials are conveyed along a moving belt and, obviously, it is impractical to move large areas of drapery material across a conveyor means when only one edge thereof is to be subjected to the bonding step.
Furthermore, the Bianchini method is expensive and inefficient. The heat which is blown across the tape for melting purposes is open to the atmosphere and, as a result, the heat is easily dissipated and thus results in an unnecessary expenditure of energy. Also, because Bianchini uses roller pairs to provide the compressive force for the bonding step, there is a tendency for the joined materials to undergo a calendering effect due to their being inclined over pressure rollers. To alleviate this effect Bianchini blows cool air over the joined material immediately after its exit from the pressure rollers. However, such an operation introduces still another step to the bonding process and adds appreciably to the overall cost of production.